Let the universal set U be the set of all integers from 1 to 15 inclusive. Define A as the set of integers in U that are multiples of 3, and B as the set of integers in U that are multiples of 5. Which of the following sets is equal to A ∩ B?
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Correct answer
A. {15}
Principle or equation
The intersection of two sets contains all elements that belong to both sets.
Why this answer is correct
A = {3, 6, 9, 12, 15} and B = {5, 10, 15}. The only element common to both is 15, so A ∩ B = {15}.
Example
If A = {2, 4, 6} and B = {4, 6, 8}, then A ∩ B = {4, 6}.
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